The present invention relates to a method for inclining a chair seat, by which the backrest side of the seat is inclined upward when being seated, and to a chair having an inclinable seat.
Conventionally, such devices where the seat is caused to move forward in line with the rearward inclination of the backrest or the backrest side of the seat is inclined downward via a complicated link mechanism have been known as structures which do not adversely influence a human body when being seated.
In the arrangements described above, a chair is internally provided with a complicated link mechanism, and the number of manufacturing process is increased causing the production work to be slowed down and the production cost to be increased.
In a case where the seat is caused to move forward in line with rearward inclination of the backrest when a person is being seated, the backbone is not allowed to be elongated, burdens are likely to be imposed on the waist, and the center of gravity is moved from the buttocks to the knee side (the load of a person being seated is concentrated at the rear side of the femoral region in the vicinity of the knee). Therefore, the rear side of the femoral region near the knee is subjected to more pressure, thereby causing the blood vessels to be pressed and the circulation of the blood to be hindered. Accordingly, such a problem exists that fatigue and sensitivity to the cold can not be eliminated.
Furthermore, in a case where the backrest side seat is inclined rearward in line with rearward inclination of the backrest, the backbone is not allowed to be elongated as in the above case, and burdens are likely to be imposed on the waist, thereby causing the degree of angle formed by the femoral region and leg to be acute and the heel to be likely to be lifted up from the floor level. Therefore, the calf of the leg is apt to be strained, and the load of a person being seated is concentrated to the rear side of the femoral region in the vicinity of the knee causing a greater pressure to be exerted at the rear side of the femoral region. Accordingly, the blood vessels are pressed and the circulation of the blood is adversely affected, and such a problem exists that fatigue and sensitivity to the cold can not be eliminated.
Furthermore, from the biotechnological standpoint, it is well known that the blood vessels are pressed by the rear side of the femoral region in the vicinity of the knees which are subject to a load (the load being given due to the body weight) when being seated, thereby resulting in fatigue and sensitivity to the cold.